There's nothing wrong with the G860; it's essentially a downclocked i3 2100 without HT. It really is by no means a bad CPU, but as your budget allows it you should get something with a bit more juice (and the i3 2100 offers just that). But, in my opinion you should look to pick up the i3 2120 at least, and preferably the i5 2300. Recommended would be the i5 2500/k, but if you are pushing for a combo meant for games that prefer a strong GPU over CPU, then your distribution of budget might be wise. Still, a i3 2120 minimum, i5 2300 recommended.

The PSU you picked or the Seasonic I linked will be enough yes. Silverstone is roughly 504W and the seasonic one is 480W output. The i5-2500k is a good choice, especially at $180. Keep in mind the k version is unlocked meaning it can be overclocked, easily hitting 4.3GHz +- you will however need/want an aftermarket CPU heatsink to if you decide to do so. You can always buy that later on though, it runs fine at stock.

updated, it looks pretty good, i would change the case though personally as i dont find nxzt to be very quality or bang for your buck but to each his own. get an i5 2500k in there and youll really be doing biz.

i would change the case though personally as i dont find nxzt to be very quality or bang for your buck but to each his own.

Besides personal taste and all that, the NZXT Gamma and Source 210 are some of the most well recommended and valued budget cases out there. I'm not saying thay are the only choice, but they are definitely good, reliable cases at that price range (unlike so many others).